The present invention relates to an manufacturing technique of a semiconductor integrated circuit device, and particularly to a technique effectively applied to a wafer cleaning technique.
For example, a scrubbing equipment provided with a brush-pressing control mechanism is a single-wafer-cleaning equipment that has a brush for scrubbing a wafer and a mechanism for pressing the above-mentioned brush against a rotating wafer at a constant pressure. There are some brush-pressing control mechanisms each of which controls a load to be applied to a brush by, for example, controlling the air pressure in an air cylinder connected with a brush holding section.
Moreover, a scrubbing equipment provided with a mechanism for discharging demineralized water from a brush is a single-wafer-cleaning equipment for cleaning a wafer by setting a demineralized-water nozzle to the inside and outside of a brush for scrubbing the wafer while discharging a constant quantity of demineralized water from the demineralized-water nozzle. To discharge the constant quantity of demineralized water, a mechanism is used which controls a demineralized-water flow rate by a flow meter connected to a pipe of the demineralized water flowing into the brush.
Moreover, there is a system for brush-cleaning the surface of a wafer while discharging chemical liquid on a wafer. This system uses a mechanism for removing foreign matters from a wafer by discharging the chemical liquid and thereby lowering the zeta potential of the foreign matters adhering onto the wafer.
Furthermore, there is a system for performing cleaning while supplying hydrogen peroxide or the like in order to remove particles transferred to a brush made of PVA.
A cleaning technique is disclosed in, for example, Japanese Patent Laid-Open No. 10-223596 which discloses a substrate-cleaning equipment having a height-position control means for lowering a cleaning tool at the time of detecting that a height position of the cleaning tool from a cleaning face is higher than a reference height in order to prevent a cleaning trouble or rebound phenomenon due to the surface-height fluctuation or the like of a wafer substrate.
Moreover, for example, Japanese Patent Laid-Open No. 10-223597 discloses that there is a problem that fluctuation occurs in cleaning because the rotational speed of a wafer differs in the central portion and circumferential portion of the wafer, and that a means for solving such the problem is a method for cleaning a substrate by monitoring the position of a cleaning face of a cleaning tool and changing pressures or rotational speeds of the cleaning tool correspondingly to the position.
Furthermore, for example, Japanese Patent Laid-Open No. 11-57632 discloses a substrate-cleaning equipment for making cleaning constant by detecting a rotary-arm position and changing rotational speeds of the rotating arm, those of a cleaning brush, or those of a spin chuck in accordance with the rotary-arm position because cleaning fluctuation occurs nearby the center and circumferential edge of a wafer.
Furthermore, for example, Japanese Patent Laid-Open No. 7-321082 discloses a brush cleaning technique having a step of simultaneously blowing cleaning liquid and gas on a rotating substrate.
Furthermore, for example, Japanese Patent Laid-Open No. 11-207271 discloses a technique for performing cleaning while hydrogen peroxide is supplied in order to remove particles transferred to a cleaning brush made of PVA.
Furthermore, for example, Japanese Patent Laid-Open No. 2000-208462 discloses a brush-conditioning technique for cleaning a cylindrical cleaning brush made of PVA, by chemicals superior to water in solubility, in order to remove dirt of the brush.
Furthermore, for example, Japanese Patent Laid-Open No. 10-294302 discloses a technique for removing floated foreign matters by rotating a cleaning brush while chemical liquid is discharged from a nozzle provided at the brush in order to effectively perform scrub.
Furthermore, for example, Japanese Patent Laid-Open No. 2000-263417 discloses a polishing technique designed so that a brush set to a dresser for removing polishing wastes passes through a position separate from the surface of a polishing surface plate and the brush is cleaned in a brush cleaning bath located on the separate position.
Furthermore, for example, Japanese Patent Laid-Open No. 10-335281 discloses a cleaning art for cleaning a brush made of PVA, by separating a wafer from the brush while cleaning liquid flows and the wafer and the brush is rotated under wafer cleaning, and thereby removing foreign matters adhering to the wafer and the brush by a centrifugal force, and temporarily cleaning the wafer and the brush, and then bringing the brush into contact with the wafer and cleaning the brush again.
Furthermore, for example, Japanese Patent Laid-Open No. 7-74134 discloses a technique for cleaning a substrate by raising a cleaning brush in a direction separate from the substrate, moving the brush to the center of the substrate, and lowering the brush while the cleaning brush is rotated without taking, in the center of the substrate, the particles having been once removed from the substrate.
The present inventors, however, have found that the above cleaning techniques have the following problems.
The first is the problem that a difference in cleaning capacity (foreign-matter removal rate) is present between the center and the circumference of a wafer. Brush cleaning is a method of forming a wafer film on a wafer while rotating the wafer, cleaning the wafer while floating the brush, the method in which the distance between the wafer and the brush greatly depends on the foreign-matter removal capacity. When the interval between the wafer and the brush is large, the foreign-matter removal capacity is deteriorated when the wafer contacts with the brush, the wafer is damaged due to transfer or the like of foreign matters from the brush. Therefore, it is necessary to keep the interval between the wafer and the brush uniform in a wafer face and keep an optimum value. However, in the case of keeping a brush pressure constant, buoyancy of the brush becomes small nearby the center of the wafer whose the peripheral velocity is small, and the brush contacts the wafer, and the wafer is damaged. To the contrary, because the buoyancy of the brush becomes large nearby the outer circumference of the wafer, the interval between the wafer and the brush increases and the foreign-matter removal capacity is deteriorated.
Moreover, in the case of keeping constant the demineralized-water flow rate from the brush, if dropping onto the wafer, the brush contacts with the wafer due to an impact of the drop and the wafer is damaged due to transfer or the like of foreign matters from the brush. To the contrary, when the demineralized-water flow rate is controlled so that the wafer is not damaged, the interval between the wafer and the brush becomes large because the water film becomes thick at the central portion of the wafer, and thereby the foreign-matter removal capacity is deteriorated.
The second is a problem due to foreign matters adhering to a brush. Because foreign matters adhere to a brush itself or the brush itself is filled with the foreign matters as brush cleaning is repeated, the foreign matters adhere onto the brush may transfer to a wafer during a cleaning process. However, when, in such a state as adhesion of the foreign matters to the wafer, the brush is brought into contact with the wafer to clean the wafer, the wafer is damaged.
An object of the present invention is to provide a technique capable of improving the foreign-matter removal capacity of a cleaning process.
Another object of the present invention is to provide a technique capable of reducing or preventing damage to a substrate during cleaning of a substrate such as a wafer or the like.
The above and other objects and novel features of the present invention will become more apparent from the description of the specification and the accompanying drawings.
The outline of a typical invention among the inventions disclosed in this application will be briefly described below.
That is, the present invention makes it possible to keep the interval between a substrate such as a wafer or the like and a brush at a constant value by regulating a cleaning condition in accordance with a cleaning state when the substrate is cleaned by a cleaning process using the brush.